The U.S. Supreme Court has struck down Florida’s bright-line standard for determining which inmates may present evidence of intellectual disability that would exempt them from the death penalty.

Florida does not consider an inmate to be mentally disabled unless he or she has an IQ of 70 or below. Those with an IQ above that line are not allowed to present evidence of mental disability. The Supreme Court in a 5-4 opinion (PDF) held the “rigid rule” violates the Eighth Amendment.

Writing for the majority, Justice Anthony M. Kennedy said the cutoff “creates an unacceptable risk that persons with intellectual disability will be executed, and thus is unconstitutional.” Kennedy found that Florida’s standard does not comply with the 2002 Supreme Court decision in Atkins v. Virginia, which held that execution of the mentally retarded violates the Eighth Amendment.

“Intellectual disability is a condition, not a number,” Kennedy said.

Kennedy said Florida’s bright-line rule disregards established medical practice because it “takes an IQ score as final and conclusive evidence of a defendant’s intellectual capacity” without consideration of other evidence. Florida’s standard also fails to recognize that an IQ score is imprecise, he said. Citing the Diagnostic and Statistical Manual of Mental Disorders, Kennedy said an IQ of 70 is considered to represent a zone of 65 to 75.

“This court agrees with the medical experts that when a defendant’s IQ test score falls within the test’s acknowl­edged and inherent margin of error, the defendant must
be able to present additional evidence of intellectual disa­bility, including testimony regarding adaptive deficits,” Kennedy said.

Kennedy also cited states’ increasing consensus on the matter: At most, nine states have a strict IQ cutoff of 70, Kennedy said.

“No legitimate penological purpose is served by executing a person with intellectual disability,” Kennedy wrote. “To do so contravenes the Eighth Amendment, for to impose
the harshest of punishments on an intellectually disabled person violates his or her inherent dignity as a human being.”

Kennedy notes his opinion uses the phrase “intellectual retardation” instead of “mental retardation,” following the terminology used in the latest edition of the Diagnostic and Statistical Manual of Mental Disorders.

The petitioner, Freddie Lee Hall, was one of two people charged in the rape, kidnapping and murder of a 21-year-old newlywed and the slaying of a sheriff’s deputy. At a sentencing hearing, Hall’s lawyers “presented substantial and unchallenged evidence of intellectual disability,” Kennedy said.

Hall’s siblings said he was slow with speech and slow to learn growing up, and other evidence suggested his mother was unsympathetic to his plight. She beat him as often as 10 or 15 times a week because he was slow and made mistakes. Many medical professionals deemed him to be mentally retarded, as did his teachers in school. Hall received scores ranging from 60 to 80 on four IQ tests, but only the last two test scores of 71 and 80 were admitted for evidentiary reasons.

Justice Samuel A. Alito Jr. wrote a dissent joined by Chief Justice John G. Roberts Jr. and Justices Antonin Scalia and Clarence Thomas.

Alito said past Eighth Amendment cases had been based on evolving standards of a maturing society, but in the present case “the court strikes down a state law based on the evolving standards of professional societies, most notably the American Psychiatric Association.”

“The court’s approach in this case marks a new and most unwise turn in our Eighth Amendment case law,” Alito wrote.

Alito also takes issue with Kennedy’s count of states with bright-line IQ cutoffs; Alito counts 10 states with an apparent bright-line rule and nine other states with unclear standards.

ABA President James Silkenat welcomed the decision, noting that the ABA’s amicus brief in the case made many of the same arguments found in the ruling. “The ABA has long taken a special interest in the equitable treatment of individuals with mental disabilities, as well as a concern that the death penalty be enforced with appropriate procedural protections and in a fair and unbiased fashion,” he wrote. “The Court’s ruling is a victory for fairness and equal justice.”